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Is there an aviation career where I would help design an entire aircraft and its systems?
If I want to design and build planes, what career would that be? Would it be a mechanical engineer, systems engineer, or what else. (I feel like saying aerospace engineer is too vague and most companies like Lockheed Martin don't have that as a job but mostly as a business unit other jobs fall under.)
Also, is there a job in which you design and build planes and pilot planes? I really want to become an engineer that designs planes but still want to pilot them as a fighter pilot or test pilot, I just want to know if there is possibility of doing both.

I'm afraid your question is just too broad, and therefore off-topic. There are too many careers in aviation, and you are basically asking for a list. Try focusing your question down some.

I meant designing everything from plane engines to mechanisms. Basically designing the plane. What other details do you want.

Sorry if I came off mean in that comment

I didn't take it that way @LukeJustin. I understand exactly what you are asking, you have an interest in an aviation career and you want to know what is out there. You are among like minds for sure, it's just that this is a forum style question, and this is a question and answer site. Questions here need to be focused and specific, or they are considered off topic.

Oh I was asking what job designs plane mechanisms such as ailerons and such.

Welcome to aviation.SE! I edited your question title to make it a little clearer what you're asking. If I got it wrong, feel free to roll back or edit again. Designing and building large aircraft is an industry, not a single job, as you said; have you considered designing kit aircraft?

Thank you for editing it. I guess I wasnt very clear. I meant helping design parts of it. For example, being part of a team that designing all the flight controls.

There's no reason why you couldn't do one thing as a job and do the other thing as a hobby (either be a pilot who builds kit planes in their shed, or be an engineer who takes up flying in the weekends). Both career paths can pay well enough to eventually fund your hobby.

@LukeJustin - sure, you want to become a mechanical engineer specializing in aviation!  Go for it!  Fortunately, you can literally google university courses for this.  However, the idea of ALSO being a test pilot or fighter pilot would be a big ask. It would not be impossible but it would just literally take a huge amount of time.  Simply, it would be like saying "I want to be a pro basketball player" (no problem, takes say 12 years of 2000 hour a year practice) AND "I want to be a doctor" (also no problem, takes about 9 years of 2000 hour a year study).  BOTH would be almost impossible.

Thank you I understand now. On a slightly related topic, what if you apply for a job at an areospace company and dont get accepted. What would you do from there. Assuming that they just wont accpet you.

@Luke Justin: If you can get a degree in say Areonautical engineering, there is a very good chance you will find a job.  Maybe not the job you want, but still a fairly well-paid job.  Try searching for things like "aeronautical engineer job market".  (Which you should really do whatever career you're considering.)

If you go the engineering route, you might be able to end up as a test-flight engineer. i.e. riding in the plane, monitoring systems while on test flights. Just not from the 2 seats up front. You're in the plane on test flights with your life on the line, you're just not in a position to attempt to save it should something go wrong </pessimistic view>

You can aspire to doing that if you want, so long as you understand the reality of the situation. These numbers are for a major aircraft engine manufacturer, not an aircraft manufacturer, but the ratio will be similar. The total number of design engineers working for the company is about 17,000. The number of those who "design complete engines" is about 10, and most of them have 20 years or more of work experience before they join that small group.

What kind of experience do you need. What kind of positions require no experience at all.

You can totally design and build your own aircraft given a big enough workshop: https://www.youtube.com/watch?v=0s8UcWU2kr8 - I suspect the career here is in the videos and ad revenue rather than anything more techincal.

@LukeJustin I think part of the reason your question was originally viewed as too broad is because it takes many people of different skill sets to design planes. The person designed the engine and the person designing the wings will have different skill sets but could both be described as "designing a plane".

Got it. Thank you!

@LukeJustin Aerospace engineering is probably the 'sexiest' engineering course at university, with far more people wanting to study it than there are jobs in the industry. The big aerospace companies recruit fresh graduates with no experience and train them on the job but only the top 5% from my course ended up in aerospace. The rest ended up in mechanical engineering or IT

If you want to design an aircraft (or parts of it), you should definitely study aerospace engineering, there you will learn about all the disciplines. If you can't find a job in the aerospace industry you can find a job in other engineering fields easily.

Not a career, so not an answer, but radio controlled model aircraft is one endeavor where people do design the entire airframe (although engines, radios and servos are purchased already made).

You probably need to create your own business. This guy isn't an engineer and it creating his own plane from scratch. https://www.youtube.com/channel/UCyEqCPjfEG1Cwt8-YEAOxbg

You were born 100 years too late.
In order to be an improvement over existing designs, airplanes become ever more complex and every detail is optimised over years and years. The days when someone like Robert Hall or Kurt Tank would design and test fly their designs are long gone.
The best you can do is to design an experimental aircraft and maybe market it as a homebuilt or a kit plane. But forget about designing front-line fighters all by yourself: This by now involves thousands of engineers and the test pilots have very different careers from those of the lead engineers.

What did you mean by test pilots and very different careers from those of lead engineers.

Test pilots normally start their careers as military pilots or engineers with lots of flying experience. Then they continue at a test pilot school for more studies and miss a lot of the experience the design engineers collect at that stage in their careers. They follow very different career paths from each other.

Even today, very small aircrafts are designed by a very small team and lead designer does have a great role, for instance, Atol aircraft is to large extend design of one man, Markku Koivurova, see   https://en.wikipedia.org/wiki/ATOL_495

@LukeJustin Either you build the rocket as an engineer or you fly in it as an astronaut.  Nobody gets to do both, not in projects with multibillion dollar budgets.

And it's best to have other people check your work, in any case. Get something wrong in this business, and lots of people can die.

Frank Robinson did most of the design of the R22 helicopter himself and tested the initial prototype himself in 1973.

Rather than being concerned with titles, let's take a look what's involved in designing/analyzing/certifying a modern airplane:

External aerodynamics: deduce the aerodynamic characteristics and propose changes in outer model line as required to achieve the desired characteristics. Skills: applied mathematics, aeronautics engineering.

Flight science: deduce the airplane performance, controllability and stability characteristics, and propose changes in flight controls/aerodynamics as required to achieve the desired characteristics. Skills: applied mathematics, aeronautics engineering.

Loads and dynamics: deduce the structural/aerodynamic coupling on the aircraft and resolve external loads on structures, control surfaces and landing gear. Skills: applied mathematics, aeronautics engineering.

Thermodynamics: deduce the heating and cooling requirements, internal gas flow, as well as anti-icing solutions. Skills: mechanical engineering.

Structure: design the internal structures that shape the aircraft, and mechanical mechanisms that perform their intended functions. Skills: mechanical engineering.

Stress: deduce the stresses inside aircraft structures and propose changes such that the relevant parts achieve the required fatigue cycles. Skills: mechanical engineering.

Flight controls (traditional): designing the mechanical/hydraulic architecture and interconnection to achieve the desired mechanical pathways for actuating flight control surfaces. Skills: mechanical engineering, hydraulic engineering.

Flight controls (FBW): designing the electrical, computing and hydraulic architectures to achieve safe and reliable actuation of flight control surfaces. Skills: mechanical engineering, electrical engineering, computer science.

Control law (FBW): designing the mathematical model and software implementation of flight control laws/autopilot to achieve precise and robust control of the airplane. Skills: electrical engineering, control systems engineering, applied mathematics.

Electrical systems: designing the high and low voltage systems that send power from electrical generators to intended areas safely and reliably. Skills: electrical engineering.

Human factors: analyzing and designing hardware/software interfaces that are intuitive, precise and robust for pilots/operators/occupants. Skills: industrial engineering.

Interiors: while often poo-pooed as not aeronautical enough, it is one of the most important selling points of an aircraft as far as occupants are concerned (especially business jets). Skills: industrial engineering, interior design.

Integration: even listing the above took some time, so it's important to elucidate, trace and validate the requirements such that when everything is put together, they fit. This may involve dozens or even hundreds of suppliers that may have limited scope to the overall design objective. Skills: systems engineering, industrial engineering

Reliability and safety: deduce the probability of failures of any system/part on the aircraft and ensure that the criticality of the failure warrants the designed probability. Skills: systems engineering.

I'm probably missing a few key areas. But as you can see, designing an aircraft is an extremely diverse endeavour that would require life-times worth of knowledge and experience. You can be an expert in any number of fields, and still make indispensable contributions to the overall design.
Experimental test pilots are probably as close as any person could to be a jack of all trades. Most test pilots I know are more familiar with the overall aircraft design and systems than most designers of their particular field(s). On top of having accumulated many flight hours (most of them military), they are well-versed in technical engineering and most of them have Masters in engineering.

Thannk you so much for putting the time into this

Yep, especially if you are just out of school, you will end up as a very small cog, doing fairly minor tasks, in very big machine.  When you get to be experienced you get to be a slightly bigger cog in your specialty, but just in your specialty.

Agree about test pilots, but even their heyday is over. There are so few of them, and they don't get to test 100+ types, amassing such a wealth of experience...

@Zeus this seems to suggest test pilots still can (and should?) test many planes, helicopters etc: https://www.youtube.com/watch?v=Evhrk5tY-Yo

@AJP, well, ideally, yes, but there's just not that many new ones being designed and flight tested during a pilot's (or an engineer's for that matter) career, and especially not such a variety of them as there was until about the 70s. This is a fairly fundamental problem, and arguably it's even more serious for engineers than for pilots.

Perhaps drones will change things again @Zeus?

Interaction design for flight controls too.

@RobinWhittleton Thanks. I forgot about human factors and interiors.

@AJP, drones are even worse: in addition to aerodynamic complexity that rivals that of a helicopter, they've got incredibly sophisticated autopilots.  The only reason they're so cheap is because the safety and reliability standards are far below those of manned aircraft.

One more "job": content creator (on Youtube or other platform). Peter Sripol built a couple of them. https://www.youtube.com/channel/UC7yF9tV4xWEMZkel7q8La_w/playlists (even though some of those are not 100% his independent designs)

I'll address the question in the title: how to get into actually designing an entire aircraft. Not every component, but making the major, visible decisions.
Such jobs do exist, but they aren't easy to get. Design is an iterative process that goes continuously more in-depth on every step. It begins with a requirements document, which are responded to with design proposals, which then get elaborated on for at least 3 steps - conceptual, preliminary, and detail design. Each step takes more than 10x the number of people than the previous.
To design the entire aircraft, or at least a large part of it, you want to be in that select 1% involved in conceptual design. For that, the primary degree to get is specifically Aerospace Engineering. Anything else, more specific, is too likely to pigeonhole you into one of the departments that do detail design work. For general design, where you'll be selecting the planform and the engines, you need breadth of knowledge more than you need depth.
Let's look at three ways to do it:

Big industry. Seems obvious, as you'll get hired right out of college, but the hard part is getting the right job. New engineers start in detail design, and most engineers stay there. For each person making major decisions, big aerospace needs 100 rank-and-file engineers that just make the 3D models and fill out the part lists.

Working your way up through promotions and lateral moves may work, but runs the added risk of getting detached from the technical work. You'll have to make yourself extremely visible, inside and outside your company, specifically showing your interest and ability to create or develop design concepts.
Most if not all large aerospace companies have a "Skunk works"-like unit, which among other things plays around with pie-in-the-sky projects. That's your goal, you have to get in. That takes reputation, and gaining it while doing your basic duties is comparable to doing a full-time job and a Ph.D. at once - in fact, one approach is to do just that. You'll have next to no free time, but I know people who have achieved this. This is a difficult approach with a slim chance of success, but the upside is that you'll be financially secure in any case; at worst you might be bored.

Startups. Starting out in as the smallest companies that still design and build aircraft is a more sure way to get to design at least something. It can be a startup that's playing with ultralights, electrics, or just unusual ideas. Such companies avoid or outsource low-level work, defer the painful weight-cutting phase, and focus on the broad strokes.

That will get you to work in a very small design team, building airplanes just as you're designing them, and possibly even flying them. To join a company like that, piloting skills can be more important than an advanced degree, and experience with homebuilts can just win them over - they're looking for enthusiasts, not 9-to-5'ers.
This path is less selective than the other two, but you better have a good plan for supporting yourself, as flight school and homebuilts will be big out-of-pocket expenses, especially if taken while in college (you want to start early, after all). In other words, it's risky. But "full-stack" design experience in a small company can then get you into conceptual design roles in progressively larger companies. Eventually you might end up leading a large project, or even running your own company - startups prepare you for that better than office work does.

Test pilot. This is less designing, more flying. Being both a test pilot and an engineer is not only doable - a college degree is already a common prerequisite for becoming a military pilot, and aerospace engineering is the perfect choice.

To get from there to being involved in design, you need to be a test pilot. This job isn't about just flying, but about evaluating the aircraft, requiring a lot of fundamental knowledge. Not all test pilots come from a military background, but military flying is a proven fast track. An advanced degree in a related field is also common for getting into a test pilot position, and it will refresh your technical knowledge.
This is less likely to get you into a decision-making role, but it can get you on the principal team, where your experience and input help drive the decisions. In smaller companies, test pilot and engineering roles can be combined. If you maintain and build upon your engineering skills, test pilot experience will also open a lot of extra doors for you - an engineer that knows first-hand how design decisions affect flight characteristics is highly useful at early design stages. Your roles will tend towards consultant rather than staff work.
To sum this up, all 3 paths start with an aerospace engineering degree. Then:

Flight school -> resume-building (homebuilts, jobs, publications, etc) -> startups (you're there, designing experimental aircraft) -> sell yourself up to design bigger things.
Requires: Lots of enthusiasm, obsession preferable.
Risks: Running out of money.
Bonus reward: The fun starts right away; lots of innovation on the job.
Industry -> advanced degree/Ph.D -> public visibility -> climb the ranks -> try for "Skunk works" style teams.
Requires: High intelligence, office skills.
Risks: Getting stuck in detail design.
Bonus reward: Big projects, lots of funding.
Military (officer) -> pilot training -> service -> advanced degree -> test pilot -> industry job. This answers your desire to build and fly planes, with a focus on the flying part.
Requires: Excellent fitness + intelligence + discipline.
Risks: Not making the cut for a pilot.
Bonus reward: Flying the coolest stuff.

None of these is likely to be a straight road. These are just checkpoints to reach; you'll do a lot of other things along the way, building up knowledge, experience, and visibility. But purposefully developing your competencies towards this goal gives you a shot.
As other answers have outlined, there's a lot of different jobs in aircraft design, and they have different requirements. Talented people can get into conceptual design from any starting point in the industry, and you may cross several disciplines. The routes above are just some of the ways to maximize your chances.
In any case, start early. Pick up some light reading, add aerodynamics, build a model plane, fly a sim, get to the real planes once you can. Make dozens of paper designs, each more detailed than the last. In college, ask the most questions, jump on every relevant project, go to every conference, take every opportunity; be a star student if you can, or at least the geek among the geeks. The kind of jobs you're after require as much knowledge about different aspects of aviation as you can get, so use the time you've got.

Thank you. Do you recommend I major in Areospace Engineering or mechnical? Whats the difference?

@LukeJustin For your goal, Aerospace all the way - it will teach you a little about everything, plus the big picture, which is what you need. If you go mechanical, you'll be able to work in a lot of fields, but your work will be designing components, not the whole thing.

While your advice is correct in general, there is a lot of potential for frustration along the way. This is everything but a straight road and will only look that way in retrospect for a select few. I have been in preliminary design jobs in two aerospace companies and we retired colleagues who had never got even one design off the ground. In their whole career!

This is an excellent answer focusing on being the technical lead on an aircraft program.  Whatever route is chosen, it is important to emphasize that you still won't feel like you designed the entire aircraft.  There will be many parts you have no idea about because the rest of the team did the work.

I think light reading would be the book on blimps.

Not for modern airplanes. Let's look at an example.
Take a small airplane, the Cessna Skyhawk.
Even on an airplane that small, Cessna doesn't make all of the components itself. For example, the engine is made by Lycoming, the avionics are provided by Garmin, the propeller is made by McCauley etc. There isn't a position at Cessna involved in the design of all the components, because Cessna itself doesn't even design all of them.
It becomes even more complex on larger and/or higher-performance aircraft such as fighter jets.
Each subsystem has become so specialized that experts in that field are required to design state-of-the-art components, and market forces make it more efficient for one company to specialize in a subsystem and provide that subsystem to all airplane manufacturers (i.e Garmin avionics) instead of each manufacturer having a small team of specialists for each subsystem.
The closest thing you could do (as others mentioned) would be to make and sell experimental kit planes, but even then you'll probably outsource at least the engine and avionics.

Probably the last guy that was able to do that successfully was Burt Rutan. A person whose history is worth studying if you are interested in this sort of thing. Designing a complete aircraft from scratch today is far less likely then designing a complete car.

This exactly. The answer to this question is: be Burt Rutan.

If to see an aircraft as a vehicle that is able to fly by gaining support from the air, the definition may cover also drones of all kinds. Then a realistic way would be to create a startup that designs a drone.
For instance, I know a Swiss startup that designed unusual VTOL fixed wing drone offering much more endurance than its helicopter-like competitors. It needed a very complex controller just to do the transition. The drone is now great in high-precision aerial surveys.
The startup has been created by a few students right from the university.

There are more than one startup in this field and common to all is a 90% software / 10% hardware workload. This is far removed from the back-of-the-pants flying of yesteryear.

At one step remove, technical computing.
Over the four years I in technical computing at BAE SYSTEMS, I was helping design:

Operational research simulation Observe Orient Decide Act loops
Sensor integration
Genetic design of wing shape
Simulated annealing of processor allocation
Structural integrity modelling
Radar cross-section estimation
Autonomous air system collision avoidance (for which I had to learn the pilot's rules of the air etc.)
Fault detection in fuel systems

Essentially the job is having enough software engineering to create tools to solve problems that the experts in these domains couldn't solve using off the shelf tools, matlab or numpy.
Each of these different topics was something I had to learn enough about to translate the different specialists' knowledge into meaningful results.
All engineers are specialists, but the only other engineers who also had to know a bit about everything were the systems safety engineers.

It's perhaps a good point, but it can go the other way too.  As a kid, I worked (just as an assistant) in the software group for just the engine development at a well-known aircraft engine research project at the time in Europe.  It was minutely specialized, all the software folks did only exceedingly specialzied stuff...

@Fattie yes, there's a big difference between embedded software and technical computing

yes, very true....you're right

As a professional engineer, as other answers have said, you will never be able to build an entire plane on your own.
Courses do exist though which allow you to study the basics of all major elements of aircraft and avionics system design, and then specialise in your chosen field. For example, this course from Loughborough University in the UK.
https://www.lboro.ac.uk/study/undergraduate/courses/a-z/aeronautical-engineering-beng/

There are many universities offering aerospace engineering courses, some of which even include flying but they produce about 10 times as many graduates as the UK has jobs for aerospace engineers.

@RobinBennett I wouldn't disagree with you there.  That's a general fault of the UK university system, which is mainly designed to occupy young people for 3 years and separate them from tens of thousands of pounds, not to prepare them for a future career.  Music Technology is even worse.  At least with aero engineering you can easily move into other areas of engineering such as automotive, control systems, or software generally.

This may be an offbeat answer to the question, but the career you're looking for is that of a YouTuber. Colin Furze is a person who designs and flies his own vehicles. It'd take a lot of media savvy, and I'd shudder to think about the economics of it, but there you have it.

Study Aerospace Engineering in Stuttgart, Germany.
You put your focus on aircraft design. The faculty designs, builds and operates its own experimental aircraft. I would guess that 40-60 % of the students have a piloting license. You can also join the Akademische Fliegergruppe Stuttgart (AKAFLIEG).
As far as I know, there are similar universities in other countries, e.g. the SUPAERO in France.

None in America? MIT? Purdue?

@LukeJustin: It would help to know where you live, but yes, there are plenty more.

I live on the east coast of the us

@LukeJustin: The punishing fees at US universities make things like Akafliegs impossible. Students have to focus on their grades so they finish with minimal debt. Being in an Akaflieg means adding maybe two years to the curriculum and skipping many classes, but learning by doing. Did it myself, so I know what I am talking about. Best you can do is to show up at one of the groups and hang out with them for some time. You will learn more in a shorter time than anywhere, but not be able to show a fancy diploma for it.


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Why do shockwaves move aft with camber/trailing edge deflection?
Why does a shockwave move further towards the trailing edge with increasing camber?
Also, is the shockwave the thing above the aerofoil or behind it?

I think there's no better explanation out there than this one. Let us know if it helps in answering your question. The shock waves is where the red zone ends toward the trailing edge. The blue zones are where speed is low, possibly detached boundary layer.

Anyway it would be nice to know the source of those two pictures: is the different airfoil the only difference among the two? Or also speed or AoA is different? Without this information is not possible to correctly answer this question.

The increased curvature of the higher camber at the end of the airfoil will keep the speed on the upper side high. As a consequence, there is little deceleration which would force a shock.
Remember that a shock in transsonic flow is the forceful ending of a supersonic pocket of air. It will be delayed until the rising pressure of the decelerating surrounding and still subsonic air makes it inevitable. Within the shock the flow accelerates in order to fill the space vacated by the thinning airfoil contour (see here for a more complete explanation) and outside of it it decelerates. That cannot last forever, but adding camber will stabilize the supersonic pocket by adding a suction area over the highly curved contour which keeps the air from decelerating as early as it does for the uncambered version.
The same, btw, happens with a downward deflected flap, because the kink in the contour at the hinge point also creates a local suction peak.

is the shockwave the thing above the aerofoil or behind it?

The shock lies in the thin line separating the dark red and green areas on the upper side of the airfoil. Its strength is proportional to the inclination of that line, i.e. it is strongest near the surface. It is, however, spread out into a triangle from the interaction between the boundary layer and the shock which makes it look like the greek letter $\lambda$, hence the name Lambda shock. This is typical for transsonic flow.

I don’t think Peter is correct here- For the flow velocity to still have increase there would have to be a favourable pressure gradient but, after point of max thickness there isn’t. Therefore even with the curvature, it wouldn’t help

After point of max thickness flow is already supersonic (dark red colour) and therefore speed does increase. If it were subsonic then you'd be right.

Sorry if one of the new writers is acting up a bit, but the question does bring some interesting aspects of airfoil design into play.
Firstly, the use of a slightly lowered trailing edge can be used to improve airflow over the upper wing by creating lower pressure behind the wing.  This will increase the lift coefficient with slightly more drag$^2$.  Nothing new there.  172 operators know it as "Flaps 10".
Why it is so important to understand this in the trans sonic realm has much more to do with controlling pitch tendencies, as the center of pressure changes, due to Mach effects.
Supercritical wings are designed to minimize, not increase, wing camber due to a phenomena known as "tuck", which can lead to an unrecoverable dive.  Tops of these wings are "flattened" to minimize shockwave formation.
The lift generation comes more from the bottom front, with undercamber in the back to balance the center of pressure.  These wings literally "surf" along on bottom pressure, not unlike their sea side counterparts$^1$.
So, from a practical point of view, that is why undercamber is seen in supercritical wings.
$^1$this is why slats and flaps are so valuable when big airliners slow down to lower Mach speeds.  Supercritical wings more closely resemble an inverted classic airfoil.  Not surprisingly, these also make for a fairly good hypersonic lifting body design.
$^2$ this is why flaps can be retracted for better climbing performance - climbing is done with excess thrust. (thrust available - drag)

What you call undercamber is called rear loading in the literature. Its reason is fairly simple: If you need to limit overspeeds, you can only add lift when the overspeeds from thickness are low, i.e. where the airfoil is thin.

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Training requirements to work for the CAA in rulemaking
For those who write regulations in the CAA, or part of the rulemaking process:
what sort of training do you require and how are these department structured?
I wanted to know more how the department responsible for rulemaking (CE 2) tasks are structured and what sort of training they normally require to enable them to  deliver sufficient and sound regulation for the CAA.

Which CAA to do you mean? For which country?

Civil Aviation Authorities (ICAO States)

You want to work for the FAA then, in the states it's not called the CAA.

Have you tried contacting the CAA in question to ask?

In Canada and I suspect most places they tend to be people recruited from the aviation industry with backgrounds in the operations, maintenance or engineering side.  I think you'll find the average employee at a regulator has a decade or more with an airline or an OEM as a tech, engineer, pilot, etc.

No 2 authorities will be the same, especially with how they're structured. As for training, they would typically have industry experience of some form, and then do specialist training as the CAA sees fit - such as regulatory processes and policy. The ones who write the final piece of regulation are lawyers.

They copy the bulk of the regulations from ICAO

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Why does an A300/310 in LAND or GO-AROUND mode have to be at least 400 feet AGL for manual control column movement to disengage the autopilot?
Each of the A300/310’s two autopilots has two modes of operation:

In CWS (Control-Wheel Steering) mode, the autopilot(s) attempt to hold the attitude that the aircraft had at the moment of autopilot engagement; if the pilot(s) change the aircraft’s attitude using manual flight control inputs, the autopilot(s) attempt to hold the attitude that the aircraft has at the moment the pilots release the controls.1
In CMD (Command) mode, the autopilot flies the aircraft automatically, based on commands from the aircraft’s FMS.23

The FMS has several modes that it can function in when commanding an autopilot in CMD mode (BASIC, ALT, LVL/CH, PROFILE, HED/SEL, NAV, VOR, LOC, TAKE OFF, LAND, and GO AROUND modes).3  In most of these modes, applying a force greater than 150 newtons to the control column will automatically disengage any autopilot(s) that were engaged in CMD mode.
Exceptions:

During glideslope capture in LAND mode, the pilot(s) can use manual pitch inputs to assist the autopilot in capturing the glideslope, helping to reduce the amount and severity of porpoising as the aircraft locks onto the glideslope signal.
In LAND and GO-AROUND modes, if the aircraft’s height above ground level (AGL) is less than 400 feet, manual pitch inputs will override the autopilot, but not disconnect it, and the autopilot will counteract the pilots’ pitch inputs using horizontal-stabiliser trim; if this situation continues for any significant length of time, it can leave the aircraft severely out of trim at a height low enough to leave very little margin for recovery.4

Originally, applying manual pitch inputs to the control column with one or both autopilots in CMD mode would not disconnect the autopilot(s), no matter what the aircraft’s height AGL was or in what mode the FMS was feeding commands to the autopilot(s).

In March 1985, an incident occurred when the flightcrew of a descending A300-600, not realising that an autopilot was engaged in CMD mode, overrode it with the aircraft in ALT mode, leading to compensatory autopilot nose-up trim commands which left the aircraft severely out of trim, sending the aircraft into a dangerously nose-high attitude until the aircraft switched to another mode and started commanding nose-down trim inputs; as a result, the A300/310’s autopilot system was modified to disengage the autopilot in response to manual pitch inputs, except in LAND and GO-AROUND modes.5
In January 1989, one of the go-around levers in the cockpit of an A300B4 was inadvertently moved during approach, sending the aircraft into GO-AROUND mode and causing an automatic pitch up and increase in thrust; the captain countered this by retarding the throttles and applying down elevator, causing the autopilot to apply nose-up pitch trim in response until it was (apparently inadvertently) disconnected.  When the flightcrew abandoned the approach, reengaged the autopilot, and increased thrust for a go-around, the aircraft pitched up dramatically and nearly stalled before the pilots were able to regain control using manual pitch trim.5  Later, in February 1991, the captain of an A310, while performing a go-around with autopilot engaged, attempted to use elevator inputs to moderate the very high rate of climb resulting from his aircraft’s light weight.  The resulting nose-up trim inputs from the autopilot, combined with the engines being at full power, caused the aircraft to climb steeply and pitch up almost to vertical, resulting in a stall and loss of control; the aircraft climbed and stalled twice more before the pilots regained control by trimming nose-down with the electric trim switches (the autopilot had disengaged during the first steep climb, but the horizontal stabiliser had already moved to nearly the full nose-up position by this point).  Following these two incidents, Airbus recommended that A300/310 operators modify the aircraft’s autopilot so that manual pitch inputs would disengage it even in LAND and GO-AROUND modes, as long as the aircraft was at least 400 feet AGL.5
On 26 April 1994, an A300-600 suffered an accidental go-around-lever activation during approach, similar to the January 1989 incident; unlike in the earlier incident, the autopilot, once engaged, was not disconnected until much later, and it sent the horizontal stabiliser to the full nose-up position, leading to a steep climb, stall, and uncontrolled descent terminated when the aircraft crashed on airport grounds, killing all but seven of the 271 on board.  The Airbus-recommended modification to the aircraft’s autopilot system had not been embodied on this aircraft; said modification was subsequently made mandatory.5

Although the situation is now much better than it originally was, why does the A300/310’s autopilot system still remain active, and trim against the pilots, if manual pitch inputs are applied below 400 feet AGL in LAND or GO-AROUND mode with one or both autopilots engaged in CMD mode?

1: Basically, the A300/310’s autopilot in CWS mode acts like SAS in Kerbal Space Program.
2: Only one of the two autopilots can be engaged in CMD mode at a time, unless the FMS is in the LAND or GO-AROUND mode; if one autopilot is engaged in CMD mode with the FMS in a mode other than LAND or GO-AROUND, and the other autopilot is then engaged in CMD mode, the first autopilot will automatically disconnect.
3: The required-control-input data from the FMS can also be fed to the aircraft’s flight-director system, allowing the pilots to fly the aircraft manually under FMS guidance.
4: To make things even worse, the pilots cannot use their yoke-mounted electric pitch trim switches to alleviate the autopilot-induced mistrim, as these switches are deactivated when one or both autopilots are engaged; instead, they must take one hand off the control yoke (while still continuing to maintain the large amount of force needed to counter the autopilot’s trim inputs) to rotate the manual pitch trim wheel mounted on the aircraft’s center console (which is mechanically connected to the stabiliser jackscrew, turns it directly, and disconnects the autopilot when used).
5: Information on all four occurrences is from the AAR for the April 1994 accident.

"Basically, the A300/310’s autopilot in CWS mode acts like SAS in Kerbal Space Program." – Except that in Kerbal Space Program, if you're flying an airplane and it's banked, SAS will apply rudder to prevent it from turning. :D

A) I'm shocked at the number of times issues were caused by professional pilots accidentally hitting levers/switches during landing. B) You'd think that close to the ground is when the human input would be most important - the computer doesn't know a car or a deer just ran onto the runway. Allowing the pilot to override and trusting the human seems to be the way to go. However, I guess that's the difference between the Boeing & Airbus philosophy. (Not trying to restart that Holy War, just thinking out loud.)

After the crash of China airlines flight 140, Airbus released an Airworthiness directive, AD (SB A300-22-6021) which made it mandatory for carriers to bring in the corrective modifications to the aircraft auto flight system within 24 months after the release of the directive. The modification allowed the aircraft autopilot to disconnect if a certain amount of force is applied to the control column above 400 ft AGL.
You can read the AD by going to the link below:
https://ad.easa.europa.eu/blob/1994-185-165%28B%29R2en.pdf/AD_F-1994-185-165R2_1
This directive however, did not enforce any amendments to the aircraft auto flight system below 400 ft. Thus, even with SB A300-22-6021 modification, if the aircraft is below 400 ft in LAND mode and if the pilot overrides the autopilot, it will continue to trim the aircraft to keep it on the scheduled flight path. If not careful an out of trim situation in this scenario is very likely. Airbus hesitated to change this, because they had concerns of a pilot overpowering the control column and disconnecting the autopilot in an automatic landing in low visibility conditions. They feared that the tripping off autopilot at such a low altitude in bad weather could make the pilots lose control of the aircraft. But changes had to be made.
So, about a year after the previous directive, in 1997 Airbus released a new AD (SB A310-22-2044). This AD enforced operators to make the modification to the aircraft which disconnects the aircraft autopilot if enough force is applied by the pilot even when below 400 AGL.
Here is the link to that AD:
https://ad.easa.europa.eu/blob/1997-373-237%28B%29en.pdf/AD_F-1997-373-237_1
The A300s and the A310s we have today have these modifications in place. So, an out of trim event in flight is highly unlikely. Below is an excerpt from an A310 manual which confirms that. The force required on the controls to disconnect the autopilot below 400 ft with LAND or GO AROUND mode is still designed to be higher than that at above 400 ft to prevent an inadvertent autopilot disconnection during an automatic landing.


text:
What are the disadvantages of having vortex generators?
I know the advantages of vortex generators (VGs): lower stall speed, lower landing and takeoff speed according to www.stolspeed.com. So what are the major reasons most GA planes and low speed ultralights don't have VGs on their wings?

Someone has ruined this question.  My answer of Cost was Not provided as a Disadvantage, it was provided to the original question of why most most GA airplanes etc. don't have VGAs.  There are NO Disadvantages to having VGs.

Cost.  A set of Micro AeroDynamics VGs can run around $1500 plus installation cost.  On my plane they are installed on the top of the wing, the sides of the vertical stabilizer (fin), and the bottom of the stabilator.  I wasn't aware there were other suppliers of STC'd VGs for certificated planes. I installed mine in early 2000s, price may have gone up some since then.
They do work well, lowering stall speed while allowing the controls to be effective the same as at higher speeds. No noticeable loss of airspeed at higher power.

I've been thinking of putting them on my plane (a homebuilt).  I can make them myself, but would have to figure out the proper chord wise location.  I think the biggest negative to them is the care required to avoid knocking them off.

They are glued in place. The only area likely to have them knocked off is  near the fuel caps if one is not careful with the hose.

Really?you can make them yourself? How?how do you cut them,how to you align them with the wings....Am gonna make vgs pretty soon and there's little resource on the internet on how to make them ,any link to help me,or article?

Check out the shapes and materials used here.  http://www.stolspeed.com/id/3  Can't help you on placement, other than what I said earlier about placement in general.

On an amateur built aircraft yes.  You can make them from T extrusions and you can buy kits for homebuilders with plastic ones you figure out for yourself. The general rule for angle I believe is 15 degrees but the tricky part is finding the right chordwise location.  The sweet spot is just before the transition from laminar to turbulent flow at stalling AOA.  If you put them too far back they don't do anything and too far forward they are less efficient.  Best thing is to look for an airplane with the same airfoil and find one that has a certified kit installed and copy that installation.

The most important reason by far is that if you design your wing (or other surface) correctly they aren't needed. Since they consume energy all the time, most manufacturers have done just that.

I would disagree with that.  VGs are beneficial to the vast majority of GA aircraft.  But they are an add-on that most people can't be bothered with.


text:
What is the aerodynamic motivation behind vortex generators?

An airplane's wing creates lift efficiently when the airflow is parallel to the chord of the wing. Vortex generators twist the airstream on the wing surface.
Doesn't this kind of twisted airflow cause lift inefficiency?

They only twist the flow in a little region just above the wing surface, whereas a substantial part of the overall lift is actually being produced by a huge package of air well above the wing being induced to move downward.  You could say they have a kind of catalytic beneficial effect much larger than their cost.
Yes there is energy consumed in making the vortex but that is usually offset by the drag reduction of the overall flow improvement achieved (they may be spinning, but the spinning air is a lot more orderly than random turbulence).  Usually VGs are used in local areas to help re-attach detached flow, but the best example of this is the popularity of VGs used as a "poor man's slat" along wing leading edges.
When aircraft have VG kits installed on the leading edges, it raises the stalling AOA somewhat less than half of what you get with a slat or slot, not bad for a row of little metal tabs.  From about 14-16 degrees for most airfoils to maybe 19-21 degrees (ballpark numbers for illustration).  On many light aircraft this is good for about 4-6 mph reduction in indicated stall speed.  On light twins VGs can also lower the minimum control speed to close to or even below the stall, a huge safety feature.  They also tend to drastically improve stall behaviour.
You would think leading edge VGs would come with quite a cruise speed penalty, but usually the penalty is negligible if at all, because there is a small drag reduction from the reduction of flow separated turbulence at cruise that offsets the energy used to create the vortices.  In a worst case, maybe a light twin with VGs will see a 3 mph hit on cruise speed, but the safety benefits are too massive for this to matter.

You are correct that vortex generators create drag, so a successful installation depends on reducing some other drag even more. Airflow separation causes significant drag that vortex generators can reduce. The energy consumed by vortex generators making drag is injected into the boundary layer, delaying airflow separation and the eventual stall, which might be of even more value. Correcting poor flight characteristics on an existing design is often where they are used. The illustration of a wing stalling is easy to understand but may not be the best use of VGs since few wings fly continuously on the brink of separation.

No.  The vortex helps keep the boundary layer attached so lift is created for a longer time as the plane slows and the wing is tilting up & back for landing.

Image source

I am going to complement previous answers about VGs. All previous three answers are showing a fact:

Given a designed wing the stall angle can be reduced and also the maximum lift can be increased.

The actual motivation to use VGs is the overall most efficient solution. Your reasoning is right, a VG is introducing drag and, for a given angle of attack a less aerodynamically efficient wing.
However, let's take the problem from a different perspective. I have an airplane that I am desiging and I have several design parameters, imagine that one of the constrains of design is that, for example, we need to be able to be able to lift the aircraft with a given weight, but that point is not the nominal point, is just one design point in the envelop you shall design for.
Essentially, at design level, you will see what is the maximum ever lift you can generate and multiply by the surface and the dynamic pressure. Dynamic pressure will be given by the design point, and your designing parameters will be surface of the wing and maximum lift.
So... you are interested in optimizing the cruise condition... obviously you will try to make that wing, for the given lift of the cruise condition, having the less drag possible.
This is bringing you to a trade off, what will providing less drag, an extra surface or a set of VGs? Given this trade-off, you've got the installation or not of VGs.
Essentially you will be using the energizing capabilities of VGs when there is a trade off in an specific condition. I have described you a condition that is sizing the size of a wing (typical from tail plane) but you can also take a look to this question where another specific condition is discussed related to the engine nacelle.

Keep in mind that the OP has been asking lots of questions re: building his own ultralight.


text:
Finding the center of gravity/centroid of an airfoil?
I'm in the process of building myself a wing frame out of balsa wood. However, as a high school student that's just started aerospace engineering, I'm not really sure how to go about it in some ways.
What I'm looking for is the center of my ribs so that I can find the best point to put my main spars in. The ribs themselves are full flat-bottoms if that helps any. Is there a go to equation for something like this?

In addition to checking out wing frame structures on the internet, why not go down to the hobby shop and get a balsa plane kit?  Airplane building is a hobby you will have all your life.
Generally, in balsa, you have a top and bottom spar, a leading edge, and a trailing edge to attach the aileron (get lots of sand paper and CA glue).  As mentioned, put you spars at around 25 - 33 % from leading edge, around the highest part of the rib.  You may also have good luck strengthening your wing by covering it with 1/16 sheet balsa, others use heat shrink monocoat.  But you must also stiffen the wing so it can not twist when you use the ailerons.  So you may wish to add balsa between the ribs connecting the top and bottom spars, creating a box structure.
A lot of ways here, and you can't read too much about it.  Please let us know how you are doing with it.  Check out RC Groups website as well.

Structurally, depending on how many spars you want to use, there are positions based on experience. For a single spar D nose construction 25-40% is a good idea.
If you want to find the centroid, I recommend you get some CAD software and draw it, and let the software find it for you, at least that way you can print out templates straight away.
If you are calculating stability, about 25% for aerodynamic center is a good estimate

If you are looking for a suitable position to build a flyable model I would suggest locating them approximately 1/4 of the chord length from the leading edge.  The rest of the airframe would need to be factored into computing the aircraft center of gravity and its relationship to your spar, but generally 25% LEMAC, (Leading Edge of the Mean Aerodynamic Chord) is a good starting point.
As a point of reference, the acceptable CG range of the C-130 Hercules is 15 to 30% LEMAC.
The center of pressure or lift of the airfoil will change somewhat with AOA, but I'm afraid that I can't help you with calculating it.


text:
What are torque events and are they very common when flying a rotorcraft?
On rotorcraft like the MD500 the POH suggests that torque events be recorded in the aircraft maintenance logbook.
What are these events, are they common and how many are typically logged during the average flight?

Most western made helicopters have limitations on the amount of engine torque to which the transmission and drive dynamic components may be subjected. Exceeding the rated torque either transiently or for a specific length of time can trigger the need for special inspections or worse, an actual maintenance evolution. Depending on make and model, short transient excursions may be allowable under certain conditions. Many, if not all, Russian made equipment have well overbuilt transmissions / dynamic components and I have heard that some don't even have torque indicating instruments. Just keep pulling collective till max engine temp or engine droop. This comes at the expense of heavier transmissions though. Hope this helps.


text:
Does contra-rotating vs regular propellers, have any effect on icing?
I am trying to understand whether can there be any correlation between the contra-rotating propellers and the ice accretion over the wing ? For instance, is there any evidence that ice accretion is more in regular propellers when compared to a contra-rotating propeller ?

Welcome to aviation.SE!

Are you concerned about total accretion alone, or are you concerned about (a)symmetries as well?

What are the parameters for icing on the wing?

temperature
air humidity
airspeed / pressure

The rotation direction of the propeller does not effect any of this parameters. Therefore the propellers rotation direction does not affect icing.

This is not true, propeller swirl means the local angle of attack of a wing behind the propeller is affected by the propeller direction and speed.

@fooot But it does that with opposite effect on either side of the propeller so when we change the rotation direction the icing may be affected locally, but for the plane as a whole the local changes level out each other.

I have not seen any engineering study or even theoritical discussion on this topic.  However I can from practical experience say contra rotating props appear to have the same propensity to ice as non contra rotating props.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Positions of drag wires in a bay
Take a good look at the small dots • on the bays of this two spar wing.
My question is:

Are the drag and anti drag wire as seen in bay 1 supposed to connect to the root of the compression tube
Or to the intersection between the wing spars and compression tube as seen in bay 2 or
are they supposed to connect to the wing spars as seen in bay 3?

In other words, which bay is set up correctly? 1, 2, or 3?
This is the point I'm at in my project, your answer will be much appreciated.

Neither. The best one would something between 2 and 3. The continuation of the wire should cross the intersection between the middle lines of the spar and compression tube.

In structures with two-force members, such as trusses and combinations of rods and beams with wires, the members are intended to work primarily in tension/compression. To achieve this, the middle lines of the cross sections of all members at a joint should intersect in a single point. If they don't, some of the members will have to carry additional loads such as bending or torsion moments.

Problems due to eccentricity at joints often show up as fatigue problems: even if the aircraft structure passes all static tests, the stresses due to the additional bending moment make the structure fail much earlier than it would have if correctly assembled/designed.

45 degree braces, especially formed as a cantilever structure, actually replaced cross wires in aircraft wing design many years ago.  But for ultra lights, this design still is around.  I would worry about wires stretching and losing tension, and yes, how to attach them.

I would have to go with 3.  It is important to determine the weakest point. Cross brace wires work in tension. In other words, any force trying to collapse the square side ways (into a parallelogram) is resisted in tension with the bracing wire.  In a wing viewed top down these would be drag (wind folding backwards) and antidrag (wing folding forwards).
Notice this is exactly the same as bracing wires for wings folding up or down
(for a biplane configuration).
Although 45 degree cross members are extremely good to hold square shape in compression (especially in wood), I would not attach a tension wire to it as it may simply
rip free.  Some type of reinforced grommet in the stronger forward and rear spars may prove
to be a better design.


text:
Is lift force less than weight during a descent?

In the above image lift is the same during a climb and during a descent. Is lift force not supposed to be less than weight during a descent?
Secondly, does descending at an airspeed much lower than the dive velocity (Vd) of the airplane affect the rate of descent of plane?

This question is misleading.  What reason is there to believe that the red arrow points to a climb and the blue arrow points to a descent?

Really the question should not be answered at all, but I did anyway.

@quietflyer There must be a chart or drawing that is not shown here. Point A probably indicates climb while point D indicates descent. Without the chart, though, you're right. A and D are not defined

I bet point A indicates maneuvering speed and point D indicates Vne-- I bet it's a V-n diagram

The content reproduced in the question is basically exploring what happens if we suddenly bring the wing to the angle-of-attack required to produce some given G-load, while flying at some given airspeed.  The value of lift given in both cases -- 4166 pounds -- is undoubtedly NOT the weight of the microlight aircraft.  It is undoubtedly much higher than the weight of the microlight aircraft.  We are NOT looking at a situation here where net force and net acceleration are zero, so this content really doesn't shed light on the questions being asked.
On the content reproduced in the question, it's not clear why the asker believes that that the red arrow points to a climbing situation and the blue arrow points to a diving situation.  At any rate, the content reproduced in the question has nothing to do with the forces in a steady-state climb or descent.
As to the questions asked--
"Is lift force not supposed to be lesser than weight during a descent?"
Yes, both in a steady-state climb, and a steady-state descent, lift is less than weight.  To understand this better, keep in mind that in the context of winged flight, lift is defined to act perpendicular to the aircraft's flight path through the airmass, not vertically.  Similarly, the drag vector is defined to act parallel to the aircraft's flight path through the airmass, and to a first approximation, the thrust vector can often be considered to also act parallel to the aircraft's flight path through the airmass.  As a result, thrust supports part of the aircraft weight in a steady-state climb, and drag supports part of the aircraft weight in a steady-state descent, and in both cases the wing's lift vector is reduced.  To see the force vector diagrams illustrating these situations, visit these related answers to related questions:
What produces Thrust along the line of flight in a glider?
Does lift equal weight in a climb?
(Note-- to apply the vector diagrams shown in the first link above to the case of a powered glide or powered dive, simply replace the label "drag" with the label "drag minus thrust" –- much as the label "thrust minus drag" appears in the diagrams in the second link above.)
"Is descending at an airspeed much lower than the dive velocity (Vd) of the airplane affect the rate of descent of plane?"
Yes, for a given throttle position or a given thrust force or a given power output, if we change the airspeed, we'll change the rate of descent.  In general the slowest descent rate is obtained flying just a little faster than stall speed.

Descending will also reduce the rate of descent due to the air density increase along the way.

For a constant (vertical-) speed descent the lift is equal to the weight of the craft.
Vertical acceleration only happens when the net vertical force is not equal to 0.
So the time when lift is less than weight is when the plane starts or speeds up the descent or stops or slows down a climb.
Similarly the lift force is only greater than the weight of the plane when the plane stops or slows down a descent or starts or speeds up a climb.

Re "For a constant (vertical-) speed descent the lift is equal to the weight of the craft.  Vertical acceleration only happens when the net vertical force is not equal to 0."-- The problem with this answer is that lift is NOT the same thing as net vertical force.  See my answer, and the associated links, for more.

First to compliment @quiet flyer for deciphering the data provided with the question.  There is nothing wrong with going to a flying school and taking a "ground lesson" if there is anything in the POH that needs explanation.
Second, to shed light on how important it is to get vector diagrams correct and account for "that which produces velocity in what direction".  This is why using gravity vector as the universal reference for direction and magnitude literally allows one to draw force vectors to scale, break them down into vertical and horizontal components, and understand what is involved with direction and speed.  Unfortunately, so many people are missing one very obvious fact, a heavier than air craft must be moving in flight, and, in an aerogravimetric enviornment, to be in steady state 0 acceleration, the thrust vector is balanced in the direction of velocity by drag.
Yes, all heavier that air craft in steady state flight need "push" to keep them moving.  DRAW IN THE THRUST VECTOR DIRECTLY OPPOSED TO DRAG VECTOR, and let's see what happens:
Parachute straight down.  Direction straight down.  Power source gravity.  Lift source drag only.  Horizontal velocity none. Drag and Gravity vectors are equal and cancel at steady state at a given velocity.
Glider descending steady state.  Direction angled towards earth. Power source gravity.  Lift source drag and airfoil. Horizontal and vertical velocity. Vertical drag component contributes to vertical lift (resists gravity). Horizontal lift component provides forward motion, balances horizontal drag component at steady state.  To the "purist" lift is less than gravity, but this is only considering the vertical component of lift!
Powered aircraft ascending.  Direction angled away from earth. Power source aviation fuel. Lift source propeller and air foil.  Horizontal and vertical velocity.  Vertical drag component OPPOSES vertical lift component.  Horizontal lift and drag components OPPOSE horizontal direction of flight.  What MUST compensate to maintain steady state flight: the thrust vector.
This contributes to vertical lift component to balance vertical drag, and to the "forward" motion component, balancing horizontal drag and horizontal lift components.
Anyone who has done near stall powered slow flight
with the engine screaming high RPMs knows what I mean.
With gravity vector constant WRT to earth, and drag, lift, and thrust expressed as vertical and horizontal components, the olde four forces of flight can be used to describe steady state flight regardless of direction.

And why not be a purist?

Btw, the case of "Anyone who has done near stall powered slow flight with the engine screaming high RPMs knows what I mean." appears to introduce the complication of the thrust line being significantly different than the direction of the flight path through the airmass-- due to very high angle-of-attack-- consider for example the case where altitude is constant (flight path horizontal) during the slow-flight maneuver-- would be interesting to know how much of the motor's "supporting" effect is due to enhanced airflow over wings and how much is due to "thrust vectoring" effect, percentage-wise.

For example how much would the minimum sustainable airspeed jump up if we took away the enhanced airflow over the wings but left the "thrust vectoring effect" in the picture, and how much would the minimum sustainable airspeed jump up if we took away the thrust vectoring effect but kept the enhanced airflow over the wings? Would be interesting to know-- video noting extreme performance of over-powered bush plane Wilga (now Draco) w/ radial engine swapped for turboprop is fascinating re extreme nose-high attitude in power-on flight near stall youtube.com/watch?v=PqhI4MeCn1c

nothing wrong at all, you did mention to Jan WRT ground and WRT plane cases.  2. That is true (propeller is also wing). 3. Now we are moving towards helicopter, no?

"To the "purist" lift is less than gravity, but this is only considering the vertical component of lift!"-- actually this is not a true statement.  Sorry to keep locking horns with you Robert but if you look at the gliding-case diagram linked in my answer you'll see that the entire lift vector, not just its vertical component, is less than weight

(In other word, the hypotenuse of a right triangle is always the longest side, and the hypotenuse is the weight vector, not the lift vector.)

Locking horns is ok in this kitchen, like your idea of putting it in the form of another question.  Let's just avoid "true or untrue" for now.  Now notice the parachute has no "pure" lift vector at all! It's all drag.  So there is certainly more than one way to descend, and I believe that has a lot to do with Vbg.  So, if you have a wing and pitch down a bit, lift vector grows.  There is no one size to It! Tx for comments.  BTW,  finishing up final landscaping and gardening touches on side force/pendulum effect hammered out here. Looks great!

I may not have time to dive back in to the pendulum/ sideforce thing for a while--

No need to.  See you next question, and BTW, I did like the way you figured what was in that POH.


text:
How to calculate the shear centre of a wing?

How is shear centre of a wings calculated? i.e. how can I calculate the wing shear centre of a two spar wing with main spar at 0% of wing chord and rear spar at 75% of wing chord? (Assuming the two spars have the same stiffness.)

I implemented a program using Matlab for S.C calculus purposes (I'm actually involved in an aircraft project and, fortunately (or not), I'm the structures guy. I have based the code and the theory in a PDF bibliography that is linked w/ the .zip folder. You'll notice two matlab codes:
-One is named "Load_Airfoil_Coordinates_using_MATLAB.m". It loads any .dat file (i.e., if you have your airfoil points, you can plot it using this code);
-Another is named "Matlab_script_for_the_shear_center.m". It calculates, beyond your airfoil's C.G (Xcg,Ycg), the shear center (Xsc,Ysc) - probably you'll need to change some of the inputs to agree with your problem, specifically. Despite I've commented the most part of this code, I recommend you to follow Perini's theory (PDF bibliography) to understand the steps.
To download the .zip folder, please click my OneDrive link: https://1drv.ms/u/s!Aqqj-vTtH2vbomM9cVTInsHp7dbn?e=PMFudZ.
If you're just focusing on the theory, I recommend you some bibliographic references, such as:

T.H.G. Megson - Introduction to Aircraft Structural Analysis

David J. Peery -  Aircraft Structures

B. K. Donaldson- Analysis of Aircraft Structures
Hope I was helpful.

Best regards,
João Cioffi

Can you update the Drive link of the code? I am trying to calculate a similar thing for the wind turbine blades.
Thank you

@SushilSharma: note that "João Cioffi was Last seen more than 3 years ago"... Most probably you won't get any feedback from him. I'd suggest you to write a new question.


text:
Finding strength of vortex by solving integration of thin aerofoil theory!

Can any one solve the upper equation from the image and obtain lower equation from image?
Image from J D Anderson 5th edition page no. 324

Have you tried it yourself? Can you explain where you're getting stuck?

Of course I have tried!

Well, there are many solutions to the first equation. We just have to find one which makes physically sense. One of the solutions to this equation has obviously* the form:
$\gamma(\theta) = 2 V_\infty \alpha \cdot\frac{\cos{\theta}-\cos{\theta_0}}{\sin{\theta}}$
Now choose a value for $\theta_0$ that satisfies the Kutta condition. The only solution is $\theta_0=\pi$. Therefore,
$\gamma(\theta) = 2 V_\infty \alpha \cdot\frac{1 + \cos{\theta}}{\sin{\theta}}$
You can check the solution substituting $\gamma(\theta)$ in the original equation. The identities

$\int_0^\pi\frac{1}{\cos{\theta}-\cos{\theta_0}}d\theta$ = 0
and
$\int_0^\pi \frac{\cos{\theta}}{cos{\theta}-\cos{\theta_0}}d\theta = \pi$

should be enough to do the check. This integrals are not the easiest, so you would need to find them in a book with trigonometric identities. There, the second one often appears in the general form $\frac{1}{\pi}\cdot\int_0^\pi \frac{\cos{n \theta}}{cos{\theta_0}-\cos{\theta}}d\theta = -\frac{\sin{n \theta_0}}{\sin{\theta_0}}$.
If you want a more formal solution I'd ask at https://math.stackexchange.com/.
*Integrating constants is easy. Therefore I transform the expression inside the integral into a constant. $g(\theta)*f(\theta)=C_1 \Rightarrow g(\theta) = \frac{C_1}{f(\theta)}$. In this case $f(\theta)=\frac{\sin{\theta}}{\cos{\theta}-\cos{\theta_0}}$

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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How many total airframe cycles should a B737-400 be put through before it becomes too costly to maintain?
I know maintenance can extend the lifespan of an aircraft but when looking at large aircraft such as the 737-300/400 is there a standard amount to go by?

For pressurized aircraft, cycles are hard limit. They are designed for certain number and after that, they must be scrapped.

According to this chart from the FAA the B737-400 variant was designed for 75,000 cycles. You can find more general info in this question as well as this discussion and this one. However there are lots of other factors that may make a 737 too costly to maintain long before it reaches the cycle life time.
Just to give an idea of flight cycles to time comparisons. Lets say a 737 flys an average of a 2 hour flight and 30 minutes to turn the plane around. 75,000 * 2.5 = 187,500. There are 8760 hours in a year so if the plane were to fly continuous 2 hour legs with 30 minutes to turn the plane around it would take 21.4 years to hit the 75,000 cycle life of the fuselage. However we all know that planes need service and most airlines dont have 100% airframe utilization all the time so it will take well over 21.4 years to hit that cycle limit.


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Is induced drag caused because of the tilt of the wing backwards?
In this question:
Why is induced drag less on a high span wing?
In the answer it was stated that wing tip vortices do not cause induced drag. If this is the case then what causes the induced drag.
Thinks about this for 10 minutes
What if the Induced drag occurs because of the tilt backwards of the wing. Do the vortices just make the induced drag worse but, not cause it.
So basically I am asking if the backwards tilt of the wing causes induced drag and how do the wingtip vortices affect the induced drag
This may sound like a duplicate of:
Is induced drag not caused by tip vortices?
but, It is not because I am asking if the induced drag is causes by the tilt of the wing. I am not asking if induced drag is caused by wing-tip vortices or not.

You are on the right track to think induced drag is a component of lift pointing backwards.

While you are not talking about wingtip vortices, doesn't this answer liked from the one in “Is induced drag not caused by tip vorties?”, together with the three more linked from there, explain it?

Or perhaps what about this answer. The question Is induced drag essentially nothing more than a specific type of form drag? is much closer to a duplicate.

I don't understand the last paragraph of the question. It might just be the grammar or it might be me.

Although your explanation isn't entirely wrong, It isn't necessarily the backward tilt of the wing, but the backward tilt of the aerodynamic force.
I look at it from two different perspectives. The airfoil is designed to accelerate air thus creating the pressure differentials that make the plane fly. The higher pressure areas will try to push the wing toward the lower pressure areas. The overall sum of these forces is called the resultant force.

That resultant force will have an amplitude and a direction or vector associated with it. The goal of designing an airfoil is to orient those forces upward to counteract gravity. So the designer will make the low pressure areas on top of the wing and the high pressure areas on the bottom to make the vector point upward. A perfect airfoil would create a vector pointing directly upward, 180° from the ground and 90° from the direction of travel. In reality, nothing is perfect, so that vector is always pointed backward to some degree. So we break that resultant force into two components. The part we're trying to accomplish, which is 90° from the direction of travel is called lift and the remaining part which is 180° from the direction of travel is called the induced drag since it is induced by the creation of lift. Even a wing producing lift at a 0° angle of attack will still produce a certain amount of induced drag.
Now we come back to your explanation. Although any time a wing is producing lift it will also produce some induced drag, as you increase the angle of attack the vector of the resultant force tilts back with it. Not necessarily at exactly the same rate, but usually not far off. Since we are still defining lift as 90° from the direction of travel and drag as 180° from it, the ratio between the two changes. For every bit of lift produced there is a lot more drag the further you tilt the wing back.

The second way of looking at it is from the inertia point of view. The intent of the wing is to accelerate air downward. Once again, a perfect airfoil would accelerate the air straight down, but in reality it will always accelerate it slightly forward also. And as you tilt the wing backwards you will produce more forward movement and less downward.

"in reality it will always accelerate it slightly forward also" - that's the clearest/most understandable explanation of drag I've seen!

@Freeman Thanks. I don't feel like I really understand something unless I can explain it to someone else

@mins Ugh, thanks for catching that vector. I'll have to go fix it in my image editor. As far as the forward part: the suction peaks that pull air downward remains in the same place with respect to the wing, so it moves with the wing. Since the suction peak is moving forward the downward accelerating air also gets dragged along with the wing somewhat. So Newton tells us that by pulling forward some on the air it also pulls backward some on the wing. Do I need to add that into the answer. Trying not to get too confusing

Now I understand what you mean. Your explanation was helpful for me.

@TomMcW The first illustration, red arrow should state "drag", not "imduced drag". In this situation there is only friction drag and a bit of pressure drag.

@Koyovis Any time lift is being generated there will always be some amount of induced drag. Other types of drag are not the result of force vector and aren't depicted. Obviously the diagrams are just to explain the concepts so the l/d ratios are exaggerated.

@TomMcW Yes I understand that it's an illustration for clarifying the terms. Hence my comment.

@Koyovis But, like I said, other types of drag are not depicted. There is induced drag in both situations

Ah if the profile is not symmetrical, yes.

You're on the right track.  Induced drag is caused by a rearward component of aerodynamic force.  And to be certain, whenever there is lift, there is drag.

The more a wing "plows" at slow speed, vs "planes" as higher speed, it will create more induced drag.

So, the wing-tip vortices just make the induced drag worse but, they are not the cause. They make it worse because they bend airflow down so the wing must be flown at a higher backward tilt. Right?

Just know that wingtip vortices contribute to the aft pointing lift.  You are right to think that the greater the angle of attack, backward tilt as you put it, the more lift will oppose the direction of flight.

A wing at AoA zero has induced drag as well. Only a symmetrical profile doesn't. As soon as lift is created there is induced drag.

@Crafterguy, wing-tip vortices, of course, do cause all of induced drag. That is because the backward tilt of the lift force is what causes those vortices! See also Is induced drag not caused by tip vortices? and How does an aircraft form wake turbulence? and the other linked material.

@STWilson, “lift” is defined as the force perpendicular to the direction of travel. So saying lift is tiltied makes no sense—the aerodynamic force is tilted. And no, wing-tip vortices don't contribute to to backward tilt of the aerodynamic force, they are caused by it.

That's great.  Edits made.  Thank you.

@JanHudec: It seems in a moment of pure absent-mindedness your wrote "That is because the backward tilt of the lift force is..." which indeed isn't what you think :)

@Crafterguy: Sadly, that is a myth that won't go away. Please stop propagating it.
see the answer and video mentioned at the end of this answer:
https://aviation.stackexchange.com/questions/36009/how-does-the-aspect-ratio-of-a-wing-impact-its-lift/44581#44581

You can say, as above, that the drag is the horizontal component of the tilt to the overall lift vector. You can just as easily say the tilt of the overall lift vector is due to the drag. So what causes the drag?
Lift is ultimately created by deflecting the airstream downwards (Newton's action/reaction law). As such, the wing is adding energy to the ambient air by deflecting it. Adding energy to the air requires energy from the aircraft. Energy is force times distance. That force is the drag.
You can get a given amount of lift by deflecting a small amount of air at a high velocity or a large amount of air at a small velocity - the change of momentum is the same (m*v is the same). But the change of energy (.5*mvv) is not - the high velocity option costs more energy so has higher drag.
So? A short wing deflects less air so does so at a higher deflection compared to a long wing. In other words, high aspect ratio wings (sailplanes) have a higher lift to drag ratio than low aspect ratio (stubby) wings, all else being equal.
All of which is why the vector points back a bit - and there's a drag component.


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How to accurately test glide ratio in given configuration?
How can glide ratio be accurately measured with typical GA airplane instruments in real conditions?
What, if any, specialty instruments are used for professional glide ratio testing (such as a manufacturer developing a new model)?
I would like to know the actual glide ratio of my airplane at several combinations of configuration and airspeed. The POH only gives the best glide distance in the clean condition.
I know there are a lot of guesses and assumptions in the pilot community, often applied far too broadly even if they can be traced to some legitimate source, but I want some real data; e.g., what is the true effect of flaps 10? Just how much is the glide ratio harmed by a 5-kt or 10-kt speed change? What is the glide angle with gear down?

GPS measures position and time.  What more would you need?

GPS is completely blind to actual wind speed and direction.

There definitely are specialized instruments for measuring drag in flight, which is directly relevant.  Google "drag rake flight testing".  (Leaving off the last two words will lead to a lot of hits on lawn tools!)  I'm not completely certain how applicable this device is to powered aircraft, but I don't see why it wouldn't be.

It is tricky to do well.
First, GPS isn't helpful because it can't account for the effects of wind.  You can fly upwind and downwind legs to try to cancel it out, but it will still be there.  We usually use airspeed and altitude instead.
The next challenge is that you want to eliminate the effects of thrust.  In a glider, this is easy.  In a powered aircraft, even when you pull back to idle, the propeller is either producing thrust or contributing to drag.
For a moment, let's assume you're in a glider -- just to get the procedure down.
Get to altitude, then pitch for some speed.  Let the phugoid damp out until you are in a stabilized descent.  Measure and record speed and rate of descent.  You'll also need to know your weight and the temperature and density of the air (OAT and PA will do).  Repeat this process for a bunch of different airspeeds.
You can process this into a 'glide polar' -- which can then be processed into a drag polar for the aircraft.  This will give L/D vs. CL.
Many approaches have been taken to eliminate the effects of thrust.  They took the propeller off of the P-51 and towed it aloft to have it glide down as one way.
The CAFE Foundation developed a sensor sensitive to the play in the propshaft -- in thrust, it is forward (one light is lit) -- in drag, it is aft (another light is lit).  The pilot would adjust throttle and/or propeller pitch until the lights were flickering back and forth.  Dig around in the CAFE Foundation's website to learn more about all that they did.
You may be interested in Lowry's 'Performance of Light Aircraft'.  It details approaches that a GA pilot can take to measure the performance of their aircraft.  Unfortunately, it is out of print and used paper copies can be pretty pricy and hard to find.  Set up an eBay search and be patient.  Or, the electronic copy is more reasonable https://arc.aiaa.org/doi/book/10.2514/4.103704

The missing prop scenario is not relevant because the aircraft has a prop. However, being at idle, power off windmilling, or dead stick might be a significant consideration, but I will just lump those into "configuration".

In a glider, this is easy. Actually, polar measuring is a contested topic in the gliding community, and historically it has happened that different measurements for the same glider do not agree as much as one would want them to.

You want the propeller stopped for best glide in a power plane with a fixed pitch prop. A windmilling prop is a powerful speed brake. On the other hand, if an engine quits at low altitude, trying to get the propeller stopped might be too dangerous. But it would be useful to know the values for both cases.
The propeller spinning with the engine at idle will be reasonably close to the drag of a stopped prop, which is significantly less than a windmilling one, and more than one turning at a "zero thrust" speed (somewhere off idle, but no way to know exactly where that is without the ability to measure thrust at the engine)
Just get it stabilized and trimmed hands off in a glide in the configuration you want, in smooth air, engine idling, and note VS and TAS.  Convert the TAS to Ft/Min, or the VS to knots, divide one into the other, and there's your glide ratio. If you want more precision, do a timed descent using the altimeter instead of trying to discern the VSI.
If you're feeling brave, you can get to a safe altitude over your airport or some other uncontrolled airport with a decent long runway, and shut the thing right down at altitude, and take your measurements with the propeller windmilling and stopped, restarting as soon as you're done, and allowing for the engine to warm up.
You might have to slow down close to stall to get it to stop, depending on how good the engine's compression is (a newer, tight engine may stop turning at or above best glide speed). If you had an engine failure at high altitude and needed to plan a long glide and needed every foot of distance because your engine quit over a glacier or a field of boulders, it might be worth the effort to get the prop stopped.

I suppose IAS along with GPS for true vertical might be the best bet. Still doesn't account for updrafts/downdrafts but picking good calm days and averaging a few runs should result in reasonable accuracy. Though I'd rather limit the number of flight hours spent on it.

Go out at 8 am when things are dead calm, and just set up a glide and time it to go from 5000 ft to 4000 ft off the altimeter to get the VS, and convert IAS to TAS and carry on from there. You will get a value good enough for any normal use. For practical application, work out the distance covered per thousand feet of altitude and memorize that.


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Stress on wing/fuselage-joint of aerial water tanker aircraft - and possible mitigating measures
Following the unfortunate crash of a C-130 aerial water tanker aircraft in Australia, a friend brought to my attention a 2002 C-130 tanker crash in the US. As can also be seen in this video, the wings fold upward and separate from the fuselage, which then rolls over and crashes.
According to the referenced Wikipedia-article, citing the NTSB (1, 2), the wing/fuselage-joint (likely) failed due to fatigue:

The NTSB investigated the crash and determined that the accident was caused by a structural failure that occurred at the wing-to-fuselage attach point, with the right wing failing just before the left. The investigation disclosed "evidence of fatigue cracks in the right wing's lower surface skin panel, with origins beneath the forward doubler. The origin points were determined to be in rivet holes which join the external doubler and the internal stringers to the lower skin panel. These cracks, which grew together to about a 12-inch (30 cm) length, were found to have propagated past the area where they would have been covered by the doubler and into the stringers beneath the doubler and across the lap joint between the middle skin panel and the forward skin panel."

This and another crash in the same year subsequently led to a fleet grounding, partially following concerns over training and maintenance.
Besides the incident referred to above, this got me thinking. The substantial and rapid change in weight when the tanker performs the drop must result in (temporary) large forces/moments on the wing/fuselage-joint. According to the summarised NTSB-report, the aircraft in the video carried some 3000 gallons of retardant (some 7000kgs at 9lbs/gallon), but does not specify volume flow. A more recent Modular Airbore FireFighting System that fits into a C-130 can disperse something under 3000 gallons in 5 seconds, yielding 600 gallons/sec - equivalent to 5400lbs or 2450kg/sec. Various comments on the YouTube-video (such as this and this) also point in that direction -- but unfortunately don't include sources. As such, I'm wondering:

to what extent these changes in weight indeed introduce forces/moments that (might) go beyond the design specifications of the aircraft?
what (technical or operational) measures are/were normally taken to prevent  such problems (structural reinforcement during the conversion, limiting 'offloading speed', no dropping during climbing/manoeuvering, etc.)?

In theory, the stresses should be considerably less than (and certainly no worse than) for a normal aircraft taking-off and landing. (When an aircraft rotates to take-off, the entire weight of the aircraft is loaded onto the wings in a matter of seconds, and conversely when the aircraft lands, the entire weight is unloaded in a matter of seconds.)

@Fiddlesticks, I follow the analogy with landing (as also pointed out in John K's answer), but I'm not sure about take-off. It seems that load change is more gradual (lift is steadily increasing with increasing $V$ and $\alpha$, up to $L > W$) than in case of a landing (although take-off weight is often higher than landing weight) or mid-air drop operation.

The problem isn't the relief of stress from dumping of loads.  If it was, you would have the same failures happening because of the act of landing, where the wing goes from being heavily loaded to unloaded in about the same amount of time.  And it's once per flight in any case and is something that all airplanes have to cope with.
Fatigue is all about the number of load cycles, the beefiness of the structure designed to handle it, and identifying the "weak links in the chain" stucturally.  The problem for tankers is they spend a large amount of time being subjected to very sharp  and relatively numerous gust loads during drop operations.  Working a fire, they are flying through extreme thermals and mechanical turbulence; it's a pretty rough ride.
So the airframes get "beaten up" you might say.  Effectively it's like taking a car that could handle the odd pot hole with no problem and driving it exclusively on a road full of potholes all the time.  Sooner or later something will break on the suspension, if you didn't anticipate the effects beforehand. And in the case of the C-130s that's about the long and short of it - they didn't anticipate the effects beforehand and the airplanes were already old.
So what happens is, the more extreme operating environment means the machine is living much closer to the margins of the original structural design analysis. This raises the risk that flaws in the original structural fatigue analysis will float to the surface, when they would normally stay dormant. Structural inspection programs that were working fine when the airplanes were being used in their normal role are suddenly inadequately frequent and/or comprehensive, and cracks form that were never a problem before, aren't being inspected for, and... ooops.
Unless you want to stop using them to fight fires, the answer is pretty simple.  These are the options:

Inspect more frequently, and or more invasively using NDT procedures.
Add more meat, or redundant meat (damage tolerance) to the structure.
Both (the probable result).

According to this article, for a BAe-146 air tanker, each flight cycle on a typical mission is equivalent in fatigue life to between four and seven normal flight cycles.

The analogy of extended periods on potholed roads is an apt one, & not new. When US & Soviet airforces changed the missions for some of their bombers in the 1960s & 70s from high altitude bombing runs (because of increasingly capable anti-air missiles) to extreme low level (to avoid radar), the aircraft suffered a huge reduction in their airframe life, found after post-training inspections. The atmosphere below 10,000ft (let alone 1000ft), even away from terrain-induced turbulence or fire/hot weather-caused updrafts & windshear, is like treacle, compared to the thin, smooth gas at 30-40,000ft.

Yeah I recall that when Cessna wanted to find out how the 172 stood up over time they wanted an absolute worst case. so they found a high time airframe, something like 12000 hrs, that had been used most of its life for pipeline patrol.  Their specimen of the Chevy Impala of the skies passed with flying colours, only needing some hinge bearings.


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Strut braced or wire braced airplane wings?
For an ultralight (or other airplane designed for slow flight), would a strut-braced or wire-braced wing be more efficient aerodynamically?

Mom was an English major so I tweaked the wording. Feel free to roll back if you feel I've gone too far.

Depends on the shape.  A round 1/8" wire would have way less drag than, say, a 1" round lift strut, obviously.  And the same for a streamlined wire vs a streamlined lift strut. So looked at that way, the wires win aerodynamically even with 4 wires per wing vs 2 struts.
However, streamlined wires are crazy expensive and have to be custom made, so they aren't really a practical option and you are stuck with round cable, whereas a streamlined strut is not so hard to do.
So the practical comparison is round wire vs streamline strut.  A teardrop shape has 1/12th the drag of a round shape, so a round shape of 1/8" diameter has the same drag as a 1.5" thick teardrop shape.
In view of that, a streamlined lift strut of say, 1" thickness (frontal area) would still have less drag than a 1/8" cable of the same length, and you only have 2 per wing vs 4 cables per wing, so overall you are ahead with streamlined struts.  Add the benefits of rigidity, ease of assembly, looks, etc, and streamlined lift struts are a no brainer, which is why 99.9% of non-cantilever monoplanes use struts (wire bracing may be somewhat lighter however - or maybe not).
Now, a streamlined aluminum extrusion for an ultralight might also be somewhat expensive to source, though nowhere near as bad as streamlined cables.  So for an ultralight, unless teardrop extrusion is available cheap, the most efficient all round choice would be to design a lift strut made from round aluminum tubing and apply over that a light fairing of .016" aluminum, or formable plastic, or fiberglass, or whatever, to get the teardrop shape.